An electrochemically fabricated ZIF-67/[HOEMIM]BF4 coating for the solid-phase microextraction and detection of polycyclic aromatic hydrocarbons.

Coatings are considered to play a crucial role in solid-phase microextraction (SPME). In this work, a novel coating named ZIF-67/[HOEMIM]BF4 was fabricated through in situ potentiostatic electrodeposition in methanol solutions containing ZIF-67 precursors and 1-(2'-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([HOEMIM]BF4). Compared with the traditional solvothermal method, this method reduced the synthesis time and enabled ZIF-67 to grow directly on the surface of stainless-steel wire, effectively simplifying the preparation process and improving the coating reproducibility. Owing to the inherent characteristics such as high porosity and high thermal and mechanical stability, and the impressive morphological regulation and extraction function of [HOEMIM]BF4, the developed coating exhibited a prolonged service life and a better extraction capacity for trace polycyclic aromatic hydrocarbons (PAHs) compared to single ZIF-67 and commercial fibers. Under the optimal conditions, the linear range of the ZIF-67/[HOEMIM]BF4-based SPME-GC method was 0.01-500 µg L-1, and the detection limit was 0.27-5.2 ng L-1. When applied in the determination of PAHs in a real water sample, recoveries between 85.6-117.3% were obtained, indicating the potential of ZIF-67/[HOEMIM]BF4 in the high efficiency SPME and GC analysis of PAHs.

A magnetic porous carbon material derived from an MIL-101(Fe) complex for efficient magnetic solid phase extraction of fluoroquinolone antibiotics.

Extraction and determination of trace hazardous components from complex matrices continue to attract public attention. In this work, magnetic porous carbon (MPC) was prepared for efficient magnetic solid phase extraction (MSPE) of fluoroquinolone (FQ) antibiotics in food and water samples. To prepare the MPC, an Fe-based metal-organic framework (MIL-101(Fe)) was grown on a network of graphene oxide and multi-walled carbon nanotubes through a hydrothermal method, and then a carbonization process under a nitrogen atmosphere was carried out to obtain the MPC with high specific surface area and good magnetism. Four target FQs including ciprofloxacin (CIP), enrofloxacin (ENO), lomefloxacin (LOM) and ofloxacin (OFX) were enriched using the as-prepared MPC and determined by coupled high-performance liquid chromatography. Under the optimal conditions, the established MSPE-HPLC-UV detection method exhibited a linear range of 0.5-800 µg L-1 and detection limits of 0.11-0.18 µg L-1 with relative standard deviations (RSDs) of 0.5-4.8%. When applied in the determination of the above four FQs in real samples such as lake water, milk and pork, good recoveries between 85.2 and 103.7% were obtained, and the RSDs were less than 4.8%. This work indicates that the MPC material can be a good adsorption material and has good application prospects in antibiotics enrichment and/or removal from complex samples.

Sensitive dual-mode detection of carbendazim by molecularly imprinted electrochemical sensor based on biomass-derived carbon-loaded gold nanoparticles.

A dual-mode electrochemical sensor was fabricated for carbendazim (CBD) detection. Biomass-derived carbon loaded gold nanoparticles (AuNPs/BC) were firstly coated on a glassy carbon electrode (GCE), and then molecularly imprinted polymer (MIP) of o-aminophenol was prepared on the resulting AuNPs/BC/GCE through electrochemical method in the presence of CBD. The AuNPs/BC had excellent conductivity, large surface and good electrocatalysis, while the imprinted film presented good recognition. Thus, the obtained MIP/AuNPs/BC/GCE exhibited sensitive current response to CBD. Furthermore, the sensor displayed good impedance response to CBD. Hence, a dual-mode detection platform for CBD was established. Under optimum conditions, the linear response ranges were as wide as 1.0 nM - 15 µM (by differential pulse voltammetry, DPV) and 1.0 nM - 10 µM (by electrochemical impedance spectroscopy, EIS), and the detection limits for these two methods were as low as 0.30 nM (S/N = 3) and 0.24 nM (S/N = 3), respectively. The sensor also had high selectivity, stability and reproducibility. The sensor was applied to detect CBD in spiked real samples, including cabbage, peach, apple and lake water, and the recoveries were 85.8-108% (by DPV) and 91.4-110% (by EIS); the relative standard deviations (RSD) were 3.4-5.3% (by DPV) and 3.7-5.1% (by EIS), respectively. The results were consistent with that obtained by high-performance liquid chromatography. Therefore, this sensor is a simple and effective tool for CBD detection, and it has good application potential.